docs: def map_get(self, key, mapkey):
          """
          Retrieve a value from a map.
  
          :param str key: The document ID
          :param str mapkey: Key within the map to retrieve
          :return: :class:`~.ValueResult`
          :raise: :exc:`IndexError` if the mapkey does not exist
          :raise: :cb_exc:`NotFoundError` if the document does not exist.
  
          .. seealso:: :meth:`map_add` for an example
          """
          op = SD.get(mapkey)
          sdres = self.lookup_in(key, op)
          return self._wrap_dsop(sdres, True)